Orbitofrontal Cortex & Executive Function Flashcards
1
Q
OFC vs PFC
A
- general consensus = regions in lateral/medial PFC (DLPFC/VLPFC/ACC) are doing something dif from orbitofrontal cortex (OFC)
- aka. cold VS hot cognition
2
Q
BECHARA ET AL. (1994): PROCEDURE
A
- looked at role of orbitofrontal cortex in cognitive control via IOWA gambling task
- pps presented w/4 virtual card decks on computer screen; told that each time they choose a card they’ll win game money BUT sometimes choosing a card loses money
- game goal = win as much as possible
- decks differ in trial numbers over which losses are distributed aka. some decks = “bad”/”good” as they’ll lead to eventual loss/win
3
Q
BECHARA ET AL. (1994): RESULTS
A
- normal controls learned to avoid risky decks & chose decks w/overall profit
- patients w/lesions to occipital/temporal/dorsolateral prefrontal cortical regions = equivalent performance (usually preferring “good” decks)
- BUT patients w/OFC lesions = pref for risky decks aka. unable to learn about response-reward contingencies
4
Q
BECHARA ET AL. (1996)
A
- tested skin conductance response (SCR) of OFC lesion patients performing same card-game task from previous studies
- SCR = sweating measure checking anxiety
- SCRs during reward/punishment = roughly equivalent in patients/controls
- BUT anticipatory SCRs (measured between deck choice & receipt of reward/punishment) = greatly reduced in patients w/OFC lesions
5
Q
DAMASIO: SOMATIC MARKER HYPOTHESIS
A
- focus on OFC role in value-based decision making
- emotional info (as physiological arousal) is needed to guide decision making
- somatic markers = bodily reactions to emotional stimuli
- OFC supports learning of associations between somatic markers/complex situations
- OFC can use said info to access likely outcomes of beh choices
6
Q
IOWA GAMBLING TASK (IGT): LIMITATIONS
A
- cards = presented in fixed order inducing pref for risky decks (aka. wins experienced early; losses experienced later)
- pps must overcome said pref & switch to “good” decks to perform well on task
- this inhibition/switching process = reversal learning
7
Q
FELLOWS & FARAH (2005)
A
- standard IGT = risky deck loss experienced later (reversal learning required)
- variant IGT = risky deck loss experienced earlier (no reversal learning)
RESULTS - VMF patients = impaired relative to controls on standard IGT
- impairment disappears in variant IGT
- suggests deficit is in reversal learning > broad value-based decision making
8
Q
FELLOWS & FARAH (2003): PROCEDURE
A
- further investigated previse role of OFC in value-based decision making
- reversal learning task = pps learned which card predicts reward then contingencies shifted
- included patients w/DLPFC/ventromedial (OFC) lesions
9
Q
FELLOWS & FARAH (2005): RESULTS
A
- DLPFC = unimpaired
- OFC = specific deficit at reversal stage
- could learn initial response contingencies BUT had issues learning about new contingency
- researchers argued that OFC = necessary NOT for learning about stimulus-reward contingencies but for unlearning established associations
10
Q
O’DOHERTY ET AL. (2001): PROCEDURE
A
- neuroimaging evidence supporting that OFC may be divided according to dif functions
- pps performed probabilistic reversal learning task; rewarded for choosing 1 reward but punished for choosing the other
- contingencies changed post learning reward option; had to learn responses to other stimulus
11
Q
O’DOHERTY ET AL. (2001): RESULTS
A
- dissociable regions of OFC responded preferentially to rewards/punishments:
1) medial OFC = stronger response to reward
2) lateral OFC = stronger response during punishment (just pre reversal) - suggests that dif regions in OFC respond to dif outcome types
12
Q
CHUDASAMA ET AL. (2017): PROCEDURE
A
- limitation for reversal learning hypothesis
- monkeys w/OFC lesions don’t always show reversal learning deficit
- monkeys had to select large/small reward (ie. 4 peanuts VS 1 peanut) aka:
1) selecting small reward -> gives big reward
2) selecting big reward -> small reward - task requires overcoming innate pref for larger food rewards aka. dif to standard reversal learning task involving learning/suppression of arbitrary stimulus-outcome relations
13
Q
CHUDASAMA ET AL. (2017): RESULTS
A
- monkeys took long time to learn task (50 sessions)
- reversal learning takes place over much shorter time periods
- aka. OFC may only be required for reversal learning when stimulus-outcome computations = made “on-the-fly” & suppression involved arbitrary stimulus-outcome relations
14
Q
OFC: COMPUTATION VALUE
A
- recent OFC function POVs emphasise computation value
- OFC = “accountant” converting info about outcomes (prob/magnitude/costs/etc) into “common neural currency” on which to base choices
- may account for OFC role in generation of complex emotions (ie. regret)
15
Q
CAMILLE ET AL. (2004): PROCEDURE
A
- OFC x neglect
- pps chose 1/2 wheels w/dif winning chances
- either got:
1) partial feedback (found out they won & know possibilities if they chose other wheel BUT don’t know what they’d’ve won if they chose the other)
2) full feedback (found out what they won & what they would’ve won if they’d chosen other option) - asked pps to rate satisfaction lvl upon outcome
